Of the various methods that may be used to apply a pattern of colorants (dyes) to a textile web, arguably the most versatile method involves the pixel-wise application of various measured quantities of dyes, under the control of a computer containing a patterning program, to form multi-colored patterns using a predetermined set of primary or process colors. Examples of such pattern generation techniques may be found in commonly assigned U.S. Pat. Nos. 3,942,342; 3,969,779; 4,033,154; 4,116,626; 4,545,086; 4,894,169; 4,984,169; 5,128,876; 5,136,520; 5,142,481; 5,195,043; and 5,208,592.
Although a variety of patterning machines may be used to practice the teachings herein, it is important that the patterning machine be capable of applying colorants in accordance with electronically-encoded patterns and patterning instructions that are based on the pixel-wise assignment of various colors to the substrate to be patterned. Machines embodying the patterning techniques described in the above-listed patent documents are particularly well-adapted for patterning textile substrates in this manner.
Such machines consist fundamentally of a plurality of fixed arrays of individually controllable dye applicators or jets, each array being supplied by a respective liquid dye supply system carrying liquid dye (known as a “process colorant”) of a specified color (known as a “process” color). Because the jets on each array are capable only of dispensing the liquid dye supplied to that array, the maximum number of different colorants that can be directly applied to the substrate by the machine (i.e., the maximum number of process colors) in a given pass can be no greater than the number of arrays. However, as will be explained below, the number of colors that can be made to appear on the substrate can be much larger than the number of process colors. As used throughout, the terms “process colors” and “process colorants” shall be used interchangeably, with the context indicating when the physical colorant in intended and must be inferred.
The arrays are positioned in parallel relationship, spanning the width of the path taken by the substrate to be patterned (i.e., generally perpendicular to the direction of web travel). As the substrate moves along its path, it passes under each of the arrays in turn and receives, at predetermined locations on the substrate surface (i.e., at the pixel locations specified by the pattern data), a carefully metered quantity of dye dispensed from one or more of the dye jets spaced along the array. The control system associated with the machine provides for the capability of delivering a precise quantity of dye (which quantity may be varied in accordance with the desired pattern) at each specified location on the substrate as the substrate moves under each respective array, in accordance with electronically-defined pattern information.
To facilitate the descriptions that follow, different definitions of “color” will be referenced. The term “target color” will refer to the desired color to be reproduced on the substrate. The term “process color” will refer to the inherent color of the individual, unblended dye or other colorant that is supplied to each of the individual dye jets comprising a given array, and that may be directly applied in pixel-wise fashion to the substrate. Note that the same process color may have a different visual appearance on different substrates, due to inherent substrate color, substrate texture, etc. Collectively, the assortment of process colors available for use by a pattering device at any given time is referred to as a “colorway.”
Consistent with the above, as used herein the term “pixel” shall refer to the smallest area or location in a pattern or on a substrate that can be individually addressable or assignable with a given color. Alternatively, if clear from the context, the term “pixel” shall refer to the smallest pattern element necessary to define the line elements of the pattern to a predetermined level of detail, analogous to the pixel counts in imaging device resolution specifications (e.g., 1280×1024). It is assumed, unless otherwise stated, that the pixels that comprise the desired pattern correspond to the pixels into which dye may be delivered on the substrate by the patterning device.
Among the techniques used by the applicant in jet dyeing or printing to extend the range of reproduced colors from a limited number of process colors (e.g., the number of gun bars in the patterning apparatus) are two techniques that shall be referred to herein as dithering techniques and in situ bending techniques. Either of these two techniques are well suited to systems in which the observed patterns are comprised of small quantities of colorant that are deposited in contiguous, pixel-wise fashion, across the surface of the substrate.
Dithering techniques are based upon the phenomenon that a color for which no exact match is available among the process colors can be visually approximated, frequently to a high degree of accuracy, by the juxtaposition of several individual pixels, each having a color that expresses a visual component of the desired or target color. When viewed at an appropriate distance, the eye tends to visually integrate or blend the individual contribution of each pixel in this group of adjacent pixels and provides the perception of a color that has been “constructed” from an imperceptible mosaic of related colors. As used herein, halftone methods (e.g., checkerboard patterns of colors that yield a representation of a desired color that is unavailable as a process color) shall be considered a form of dithering.
The term “perceived color” shall refer to the color of a small area of a substrate in which a target color has been simulated using dithering techniques, wherein the colors of adjacent individual pixels are visually integrated by the eye of the observer to form a visual blend. For example, generating the color green can be achieved by constructing an array of alternating blue and yellow pixels in a mosaic or checkerboard pattern. At a distance beyond which the individual blue and yellow pixels can no longer be perceived, the result is an area having a surprisingly uniform green coloration.
Generalizing this technique to accommodate unequal proportions or distributions of pixels that share a common color, a wide variety of colors can be generated using various arrangements and relative proportions of pixels that collectively are of two or more colors. For example, various shades of green can be reproduced with appropriate arrangements and relative proportions of blue pixels and yellow pixels. Similarly, given the availability of a “medium” blue as a process color, a variety of shades of blue, ranging from a powder blue (light blue) to a navy blue (dark blue), can be reproduced (when viewed at an appropriate distance) by using various arrangements and proportions of pixels that are colored white and blue (yielding a light blue) and black and blue (yielding a dark blue), with the relative number of white or black pixels comprising the mosaic determining the perceived relative lightness or darkness of the overall dithered pattern area. In connection with such dithering or halftone techniques, the term “heather” or “stipple” shall be used to describe the relative granularity of the image, where the eye is able to distinguish the individual pixels or groups of pixels that comprise the mosaic (i.e., dithered) area.
As distinguished from dithering techniques, in situ blending techniques do not depend upon the formation of a mosaic of different pixels that must be visually integrated to form the desired target color. Rather, these techniques strive to form the desired color on the substrate through the physically mixing or blending of the applied liquid colorants in a pre-defined area (e.g., within a pixel) on the substrate.
The creation of various colors on such substrates with liquid dyes, particularly using the dye injection method described above, is greatly influenced by the generally absorbent nature of textile substrates. Accordingly, it should be understood that, as used herein, the term “concentration” is intended to refer to the relative volumetric absorption of liquid colorant by the substrate (i.e., the degree of physical saturation), and not the relative dilution or chromophore content of the liquid colorant—i.e., a colorant applied to a pixel at a 50% concentration means that the substrate area defined by that pixel has only been saturated to one half its capacity to absorb colorant, and additional colorant(s) may be applied to that pixel without exceeding the absorptive capacity of the substrate at that location.
The term “blended color” shall be used where quantities of two or more colorants occupy at least portions of the same pixel-sized location on a substrate; the term “blended color” shall refer to the color of the physical combination or in situ blending of those two or more colorants, as viewed at the individual pixel level. Accordingly, if the color green is to be reproduced in a given area and only yellow and blue colorants are available as process colors, the designer may (providing the patterning device is capable) elect to construct that green by delivering a predetermined quantity of yellow as well as a predetermined (and not necessarily equal) quantity of blue, in a specified sequence to each pixel comprising the “green” area rather than constructing the green using the dithering (checkerboard or mosaic) method described above. By varying the sequence and relative proportion of the component colorants that are delivered to the same pixel and allowed to mix, a variety of shades or hues may be reproduced. Unlike the use of dithering, where the target color exists only in the eye of the observer, rather than on the substrate, in situ blending techniques are capable of generating individual pixels in which the colors are in fact distinctly different from the process colors, and that may provide for the accurate reproduction of the target color without the need for dithering.
Where an extremely broad range of target colors must be available from the use of a limited number of available or primary colors, i.e., from a limited colorway, it has been found advantageous to combine these techniques, thereby forming dithered structures that are comprised of individual pixels in which in situ blending may have occurred. Such in situ blending may be the result of migration of colorants from one pixel containing a colorant to an adjoining pixel containing a different colorant (“inter-pixel blending”), the placement of two or more different colorants within the same pixel (“intra-pixel blending”), or a combination of these two techniques, in which the inter-pixel colorant migration involves at least one pixel into which two or more individual colorants have been delivered by the patterning device. This provides for the possibility that, within a dithered structure, some pixels may carry the color of a process color, while others, in a proportion dictated by the relationship between the target color and the process colors, may carry a color that is the result of the physical blending of two or more of the process colors.
A specific embodiment of such in situ blending involves the oversaturation (i.e., more than 100% concentration) and undersaturation (i.e., less than 100% concentration) of adjacent pixels. If the quantity of colorant applied to a pixel area exceeds the ability of the substrate to absorb it, effectively oversaturating that pixel area, some quantity of colorant tends to diffuse or migrate beyond the boundaries of the pixel area to which the colorant was applied and occupy a portion of an adjacent pixel area, especially if that adjacent pixel area is relatively undersaturated, i.e., it has retained some unused colorant absorptive capacity. By providing an adjacent pixel area that is relatively undersaturated, it is possible to induce colorant migration from areas in which the colorant concentration (i.e., substrate saturation level) is excessively high to areas in which the colorant concentration remains below the saturation capacity of the substrate.
This migration of colorant will cause either a displacement of the color in an adjacent pixel area or a physical blending with the color in an adjacent pixel area. This migration can occur from pixel to pixel within a group of adjoining or contiguous pixels, as well as outwardly beyond the edge of the group, thereby causing colorant displacement or blending within the group as well as in areas immediately adjacent to the group. A group of adjoining or contiguous pixels containing at least one oversaturated pixel area and at least one adjoining or contiguous undersaturated pixel area (the respective numbers do not have to be equal), and which exhibits pixel-to-pixel colorant migration within the group, is herein defined as a metapixel.
Because it is frequently undesirable to oversaturate large areas of the substrate with colorant, the quantity of colorant directly applied to the adjacent pixels can be adjusted to accommodate the inter-pixel colorant migration in order to maintain the desired degree of average local substrate “wet out” or saturation level (i.e., concentration). This level is usually “100%” or full saturation without oversaturation, a level which generally assures full colorant penetration and maximum “cover.” Generally, it is preferred that the overall level of oversaturation in a given localized area be balanced by a corresponding degree of undersaturation in the same area. Thus, if a given pixel is oversaturated to a level of, say 140%, one can establish, for example, one adjacent pixel with a concentration (i.e., saturation) level of 60%, or, alternatively, one could establish two adjacent pixels, each with a concentration level of 80%.
It should be noted that, in addition to oversaturating certain pixels with a single colorant, it is possible to achieve an oversaturated condition using partially saturating applications of two or more colorants within the same pixel. Doing so will generate a blend of the colors within the pixel, and will cause an inter-pixel migration of a combination of these colorants, again creating color blends that are beyond existing color generating techniques. Similarly, separate, partially saturating applications of two or more colorants can be assigned to a pixel that remains undersaturated. Such undersaturated pixel may remain undersaturated, or may play host to the migration of one or more colorants from an adjacent oversaturated pixel, perhaps reaching full saturation in the process, as the pixel-wise patterning instructions, and the underlying artistic considerations, may dictate.
It is also contemplated that the physical placement or arrangement of the individual component pixels—including those that are oversaturated or undersaturated—within the metapixel need not be fixed, but can be varied as needed to assist in emphasizing pattern boundaries, adjusting pattern definition, or for other reasons. The skillful construction and arrangement of the metapixel—including the adept choice of the initial colorants used, careful selection of the nature and degree of colorant oversaturation and migration employed, and the judicious placement and optimal systematic rearrangement of the individual pixels within the metapixel—can greatly expand the effective color palette possible from a given number of available colors and a limited ability to apply small quantities of colorant.
It should be understood that the techniques described herein are not limited to the specific in situ blending processes or blending patterning systems described above. For example, an arrangement of liquid colorant (e.g., dye) applicators, perhaps grouped in terms of color to be applied, may be physically moved or traversed across the path of a sequentially indexed substrate while dispensing measured quantities of dye. Although such arrangement is distinct from the fixed array systems discussed above, it is believed that the teachings herein are fully applicable to and adaptable for use with such systems, provided dye or colorant delivery can be controlled at the individual pixel level.
The techniques described herein are applicable to the patterning of a variety of substrates, but will be described in terms of an absorbent substrate such as a textile substrate. Such substrates can be, for example, tufted or bonded floor covering materials. Dye application techniques that may be considered include, but are not limited to, silk screen printing, offset printing, and various methods in which a stream of dye is directed onto the substrate surface. While the techniques described herein can be used in conjunction with a variety of printing systems, they are particularly well suited to systems in which the dyed image is formed by the precise delivery of an individually specified aliquot of liquid dye to a predetermined location (i.e., the pixel to be colored) on the substrate surface, such as those described in the commonly-assigned U.S. Patents referenced above. It should be understood that other textile substrates, such as decorative or upholstery fabrics, or other absorbent substrates, may also be used.
As is apparent from the foregoing discussion, it would be highly desirable to reproduce a wide range of colors from a minimum number of process colors. Although the use of dithering or in situ blending techniques are effective in greatly expanding the range of possible colors obtainable from a given set of process colors, the choice of such process colors—the specific colors of the process dyes—has been found to have a dramatic effect on the range of colors that can be achieved with a relatively limited number of process colors. Accordingly, it is believed that the process color sets described herein will allow for the reproduction of an unexpectedly large and unprecedented range of colors, particularly when used with the blending techniques described herein.
In one preferred embodiment, a jet dye patterning device is operated with process colorants that correspond to the respective primary colors of the additive (i.e., Cyan, Magenta, Yellow, or “CMY”) and subtractive (i.e., Red, Green, Blue, or “RGB”) systems to generate color, with the optional addition of one or more commonly-used neutral colors (e.g., black, beige, gray, and/or white). This yields a total process color palette or colorway comprised of cyan, magenta, yellow, red, green, blue, and one or more optional neutral colors. As a practical matter, the total number of process colors is preferably no greater than the number of individually available colors that can be placed on the substrate of interest in a single pass through the patterning device. In the patterning device disclosed in the U.S. patents referenced above, that number would correspond to the number of available gun bars.
Pre-specified in situ blended combinations of these process colors, assuming blends of 50/50 (i.e., sequential applications of two different colorants, each at a 50% concentration or relative saturation level) or some other proportion, also can be used as colors available to color individual pixels and therefore can be used effectively to augment the selected process color palette. In this embodiment, the individual process colors and the appropriate blends of such colors, taken together, comprise the total color palette available for coloring individual pixels. It is this palette, and dithered constructions using this palette, that support the range of colors that are available to the designer of patterns to be used on the substrates of interest, and that comprise an important aspect of the development described herein.
Additionally, in another embodiment, combinations of relatively dilute and concentrated colorants having a similar hue or inherent “color” (e.g., pink and red, or gray and black), or the use of a neutral diluent (which may be clear, white, light gray, light beige, brown, black, or other neutral “color”) to generate in situ mixtures on the substrate that simulate such relative dilute/concentrated color pairs can be used if additional process colorant capacity (e.g., additional gun bars) is available. It has been found that the use of such dilute/concentrated color pairs can also serve to expand even further the range of the target colors that can be reproduced from certain palettes disclosed herein, especially when a relatively wide range of colors must be generated from a limited number of process colors.